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Showing content from https://github.com/pact-foundation/pact-workshop-jvm-spring/tree/step2 below:

GitHub - pact-foundation/pact-workshop-jvm-spring at step2

Example Spring Boot project for the Pact workshop

This workshop should take about 2 hours, depending on how deep you want to go into each topic.

This workshop is setup with a number of steps that can be run through. Each step is in a branch, so to run through a step of the workshop just check out the branch for that step (i.e. git checkout step1).

JDK 17+
Docker for step 11

NOTE: Each step is tied to, and must be run within, a git branch, allowing you to progress through each stage incrementally. For example, to move to step 2 run the following: git checkout step2

There are two components in scope for our workshop.

Product Catalog application (Consumer). It provides a console interface to query the Product service for product information.
Product Service (Provider). Provides useful things about products, such as listing all products and getting the details of an individual product.

Step 1 - Simple Consumer calling Provider

We need to first create an HTTP client to make the calls to our provider service:

The Consumer has implemented the product service client which has the following:

GET /products - Retrieve all products
GET /products/{id} - Retrieve a single product by ID

The diagram below highlights the interaction for retrieving a product with ID 10:

You can see the client interface we created in consumer/src/main/au/com/dius/pactworkshop/consumer/ProductService.java:

@Service
public class ProductService {

    private final RestTemplate restTemplate;

    @Autowired
    public ProductService(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    public List<Product> getAllProducts() {
        return restTemplate.exchange("/products",
                HttpMethod.GET,
                null,
                new ParameterizedTypeReference<List<Product>>(){}).getBody();
    }

    public Product getProduct(String id) {
        return restTemplate.getForEntity("/products/{id}", Product.class, id).getBody();
    }
}

We can run the client with ./gradlew consumer:bootRun - it should fail with the error below, because the Provider is not running.

Caused by: org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://localhost:8085/products": Connection refused: connect; nested exception is java.net.ConnectException: Connection refused: connect

Move on to step 2

Step 2 - Client Tested but integration fails

Now let's create a basic test for our API client. We're going to check 2 things:

That our client code hits the expected endpoint
That the response is marshalled into an object that is usable, with the correct ID

You can see the client interface test we created in consumer/src/test/java/au/com/dius/pactworkshop/consumer/ProductServiceTest.java:

class ProductServiceTest {

  private WireMockServer wireMockServer;
  private ProductService productService;

  @BeforeEach
  void setUp() {
    wireMockServer = new WireMockServer(options().dynamicPort());

    wireMockServer.start();

    RestTemplate restTemplate = new RestTemplateBuilder()
      .rootUri(wireMockServer.baseUrl())
      .build();

    productService = new ProductService(restTemplate);
  }

  @AfterEach
  void tearDown() {
    wireMockServer.stop();
  }

  @Test
  void getAllProducts() {
    wireMockServer.stubFor(get(urlPathEqualTo("/products"))
      .willReturn(aResponse()
        .withStatus(200)
        .withHeader("Content-Type", "application/json")
        .withBody("[" +
          "{\"id\":\"9\",\"type\":\"CREDIT_CARD\",\"name\":\"GEM Visa\",\"version\":\"v2\"},"+
          "{\"id\":\"10\",\"type\":\"CREDIT_CARD\",\"name\":\"28 Degrees\",\"version\":\"v1\"}"+
          "]")));

    List<Product> expected = Arrays.asList(new Product("9", "CREDIT_CARD", "GEM Visa", "v2"),
      new Product("10", "CREDIT_CARD", "28 Degrees", "v1"));

    List<Product> products = productService.getAllProducts();

    assertEquals(expected, products);
  }

  @Test
  void getProductById() {
    wireMockServer.stubFor(get(urlPathEqualTo("/products/50"))
      .willReturn(aResponse()
        .withStatus(200)
        .withHeader("Content-Type", "application/json")
        .withBody("{\"id\":\"50\",\"type\":\"CREDIT_CARD\",\"name\":\"28 Degrees\",\"version\":\"v1\"}")));

    Product expected = new Product("50", "CREDIT_CARD", "28 Degrees", "v1");

    Product product = productService.getProduct("50");

    assertEquals(expected, product);
  }
}

Let's run this test and see it all pass:

> ./gradlew consumer:test

BUILD SUCCESSFUL in 2s

Meanwhile, our provider team has started building out their API in parallel. Let's run our website against our provider (you'll need two terminals to do this):

# Terminal 1
❯ ./gradlew provider:bootRun

...
...
Tomcat started on port(s): 8085 (http) with context path ''
Started ProviderApplication in 1.67 seconds (JVM running for 2.039)

# Terminal 2
> ./gradlew consumer:bootRun --console plain

...
...
Started ConsumerApplication in 1.106 seconds (JVM running for 1.62)


Products
--------
1) Gem Visa
2) MyFlexiPay
3) 28 Degrees
Select item to view details:

You should now see 3 different products. Choosing an index number should display detailed product information.

Let's see what happens!

Doh! We are getting 404 every time we try to view detailed product information. On closer inspection, the provider only knows about /product/{id} and /products.

We need to have a conversation about what the endpoint should be, but first...

Move on to step 3

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